Sensor, sensor producing method, and assembly of separator and urging member

ABSTRACT

It is an object of the invention to provide a sensor which is highly reliable, and a method or producing a sensor which is highly reliable, and which can be easily produced. A method of producing a sensor in which bending of a heater and the like hardly occur is provided. 
     In the invention, an oxygen sensor ( 1 ) has: an oxygen sensor element ( 2 ); a metal shell ( 3 ); first and second sensor terminal metal parts ( 11 ), ( 12 ); a heater ( 15 ); heater terminal metal parts ( 16 ), ( 17 ); a metal outer tube ( 21 ); and a separator ( 31 ) which is housed inside the metal outer tube ( 21 ), in which the terminal metal part ( 11 ) and the like and the heater ( 15 ) are held, and which provides insulation between the terminal metal part ( 11 ) and the like. An outer-tube butting face ( 34   a ) is formed in a flange portion ( 34 ) of the separator ( 31 ). In the metal outer tube ( 21 ), a flange butting face ( 24   b ) which butts against the outer-tube butting face ( 34   a ) is formed. Both of the outer-tube butting face ( 34   a ) and the flange butting face ( 24   b ) form an inclined face which is more radially outward positioned as further advancing toward the tip end. The separator ( 31 ) is pressed toward the rear end. The pressing is conducted by deforming the metal outer tube ( 21 ), and deforming a pressing metal part ( 41 ) which is placed around a tip end side portion ( 33 ) of the separator ( 31 ).

TECHNICAL FIELD

The present invention relates to a sensor in which a sensor element isattached to a metal shell or the like, and also to a method of producinga sensor.

BACKGROUND ART

In an internal combustion engine, for example, it is known that atechnique in which the oxygen concentration in exhaust gas, the air-fuelratio state, and the like are detected and a combustion control isconducted on the basis of detected values is very effective for energysaving, purification of exhaust gas, etc. As a sensor for detecting theoxygen concentration or the like in exhaust gas (to-be-measured gas),known is a gas sensor in which a detecting element made of a solidelectrolyte such as zirconia is used. Various improvements have beenapplied on such a gas sensor.

For example, JP-A-2001-147213 discloses a gas sensor 1001 shown inFIG. 1. The gas sensor 1001 is an oxygen sensor which is to be used inan internal combustion engine for an automobile, and has: a detectingelement 1010 having a gas-exposed portion 1011 which is to be in contactwith to-be-measured gas; a metal shell 1004 which holds the detectingelement 1010 in the state where the gas-exposed portion 1011 is exposed;and a protective cover 1002 which is disposed from the metal shell 1004to cover the gas-exposed portion 1011 of the detecting element 1010. Thegas sensor further has: two lead terminals 1071, 1072 which areelectrically connected to the detecting element 1010; plural lead wires1081, 1091 which are to be electrically connected to them, respectively;connectors 1075, 1076 through which the lead terminals 1071, 1072 areconnected to the lead wires 1081, 1091; an electrically insulativeinsulating member 1005 which provides insulation between the connectors1075, 1076, and a first metal cover 1003 in which the insulating member1005 is housed. A heater 1015 which is placed inside the detectingelement 1010 in order to heat the detecting element 1010 is connected tothe outside through a lead wire 1171 and another lead wire which is notshown.

The insulating member 1005 has: a main portion 1051 which houses a partof the lead wires 1081, 1091, 1171, the connectors 1075, 1076, and thelike; and a flange portion 1052 which is larger in diameter than themain portion 1051. The first metal cover 1003 has: a small-diameterportion 1031 having an inner diameter which is larger than the outerdiameter of the main portion 1051 of the insulating member 1005, andwhich is smaller than the outer diameter of the flange portion 1052; alarge-diameter portion 1032 having an inner diameter which is largerthan the outer diameter of the flange portion 1052; and a step portion1033 which connects the small-diameter portion 1031 with thelarge-diameter portion 1032.

In the insulating member 1005, one face (the upper face in the figure)1521 of the flange portion 1052 butts against the step portion 1033, andthe other face (the lower face in the figure) 1522 of the flange portion1052 is pressed and fixed by an elastic member 1006 which is pressinglyinserted into the large-diameter portion 1032. Namely, the insulatingmember 1005 is fixed with being clamped between the elastic member 1006and the step portion 1033 of the first metal cover 1003.

According to the configuration, unlike a conventional gas sensor, thegas sensor 1001 is not required to have a structure in which aninsulating member is fixed by combining plural covers. Since theinsulating member 1005 is fixed by using the elastic member 1006, thejoining position between the first metal cover 1003 and the metal shell1004, and the like are not affected even when the size of the insulatingmember 1005 is dispersed. Consequently, there are advantages such asthat the dimension accuracy of the total length of the gas sensor 1001can be improved.

In the gas sensor 1001, as described above, the insulating member 1005is fixed by causing the face 1521 of the flange portion 1052 of theinsulating member 1005 which face is substantially perpendicular to theaxial direction (the vertical direction in FIG. 1) to butt against thestep portion 1033 of the first metal cover 1003 which step portion issimilarly perpendicular to the axial direction. However, the outerdiameter of the flange portion 1052 of the insulating member 1005 issmaller than the inner diameter of the large-diameter portion 1032 ofthe first metal cover 1003. Consequently, there is the possibility thatthe insulating member 1005 is fixed to the first metal cover 1003 in aninadequately misaligned state where the axis of the first metal cover1003 fails to coincide with that of the insulating member 1005. As aresult, also a part of the lead wires 1081, 1091, 1171 held in theinsulating member 1005, the connectors 1075, 1076, and the like are heldwith being deviated from their original held positions, so that unwantedstresses are applied to the lead wires 1081, 1091, 1171, the connectors1075, 1076, and the like. Consequently, there is the possibility thatdefects including destruction such as bending of the detecting element1010 or the heater 1015, and breakage or disconnection of the lead wire1081, the connector 1075, and the like occur.

The gas sensor 1001 is produced in the following manner. First, theinsulating member 1005 in a state where the lead wire 1081, theconnector 1075, and the like are not housed in the member is previouslyfixed to the inside of the first metal cover 1003 by using the elasticmember 1006. Thereafter, the lead wire 1081, the connector 1075, and thelike are housed in the insulating member 1005. The heater 1015 is theninserted into the detecting element 1010, and the first metal cover 1003is fixed to the metal shell 1004.

However, the work of housing the lead wire 1081, the connector 1075, andthe like in the insulating member 1005 in the state where the insulatingmember 1005 is fixed to the inside of the first metal cover 1003 iscumbersome. It is difficult to house the lead wire 1081, the connector1075, and the like at adequate positions in the insulating member 1005.When these components fail to be housed at adequate positions, moreover,unwanted stresses are applied to the lead wires 1081, 1091, 1171, theconnectors 1075, 1076, and the like in the same manner as theabove-mentioned case where positional deviation occurs, and a defectsuch as breakage or disconnection may occur.

It may be contemplated that, conversely, the lead wire 1081, theconnector 1075, and the like are previously housed at adequate positionsin the insulating member 1005, and the insulating member 1005 is thenfixed to the inside of the first metal cover 1003. However, the leadwire 1081, the connector 1075, and the like are already housed in theinsulating member 1005. As compared with the case where these componentsdo not exist, therefore, it is difficult to pressingly insert theelastic member 1006 into the first metal cover 1003, and the work offixing the insulating member 1005 to the inside of the first metal cover1003 is cumbersome.

The gas sensor 1001 is produced in the following manner. As describedabove, first, the insulating member 1005 in which the lead wire 1081 andthe like are not housed is fixed to the inside of the first metal cover1003 by using the elastic member 1006. Thereafter, the lead wire 1081,the connector 1075, and the like are housed in the insulating member1005. The heater 1015 is then inserted into the detecting element 1010,and the first metal cover 1003 is fixed to the metal shell 1004.Depending on the housed state of the lead wire 1171 and the like housedin the insulating member 1005, there is possibly a case in which thestate where the heater 1015 to be connected to them is inclined withrespect to the axis of the insulating member 1005 is most stable.

In the production method, however, the heater 1015 is inserted into thedetecting element 1010 in the state where the insulating member 1005 isfixed to the inside of the first metal cover 1003. Therefore, theinclination of the heater 1015 is compulsively changed by the insertion.As a result, unwanted stresses are applied to the heater 1015, the leadterminals thereof, the lead wire 1171, and the like, thereby causing thepossibility that a defect such as breakage, disconnection, or bending ofthe heater occurs.

The invention has been conducted in view of the problems. It is anobject of the invention to provide a sensor that has a metal outer tubein which terminal members such as a connector are housed and a separatorfor providing insulation between the terminal members, and the like fromone another is housed and fixed, in a manner similar to the insulatingmember and the first metal cover described above, and that is highlyreliable, and also a method of producing a sensor that is highlyreliable, and that can be easily produced. It is another object of theinvention to provide a method of producing a sensor in which bending ofa heater and the like hardly occur. It is a further object of theinvention to provide an assembly of a separator and a pressing memberthat is suitable for production of a sensor.

DISCLOSURE OF THE INVENTION

The solving means is a sensor having: a sensor element; a metal shellwhich holds the sensor element; one or more sensor terminal memberswhich are electrically connected to the sensor element, and whichelongate from the sensor element toward a rear end; a metal outer tubewhich is connected to the metal shell at a tip end portion of the metalouter tube itself; and an electrically insulative separator which ishoused inside the metal outer tube, in which the sensor terminal membersare positioned, and which provides at least one of insulation betweenthe sensor terminal members, and insulation between the sensor terminalmembers and the metal outer tube, wherein the separator has: a rear endside portion; and a flange portion which is positioned on a tip end sidewith respect to the rear end side portion, and which is larger indiameter than the rear end side portion, the metal outer tube has a stepportion or an inner projection which butts against the flange portion ofthe separator, at least one of an outer-tube butting portion of theflange portion of the separator, and a flange butting portion of thestep portion or the inner projection of the metal outer tube forms aninclined face which is more radially outward positioned as furtheradvancing toward the tip end, the outer-tube butting portion buttingagainst the step portion or the inner projection of the metal outertube, the flange butting portion butting against the outer-tube buttingportion of the flange portion of the separator, and the separator isheld by the metal outer tube in a state where the separator is pressedtoward the rear end.

In the sensor of the invention, the flange portion of the separator hasthe outer-tube butting portion which butts against the step portion orthe inner projection of the metal outer tube, and the step portion orthe inner projection of the metal outer tube has the flange buttingportion which butts against the outer-tube butting portion of theseparator. At least one of the outer-tube butting portion and the flangebutting portion forms the inclined face which is more radially outwardpositioned as further advancing toward the tip end. Moreover, theseparator is pressed toward the rear end. Namely, the separator ispressed in a direction along which the outer-tube butting portion andthe flange butting portion approach each other. Furthermore, in thisstate, the separator is held inside the metal outer tube.

Even in the case where, during a process of assembling the sensor, theaxis of the separator is set to be deviated from that of the metal outertube, when the separator is pressed toward the rear end, the separatormoves along the inclined face of at least one of the outer-tube buttingportion and the flange butting portion so as to reduce the deviationbetween the axes. Therefore, the position of the separator with respectto the metal outer tube can be adequately determined, and hence also thepositions of the sensor terminal members placed in the separator can becorrectly determined. As a result, in the sensor, a defect such asdestruction of the sensor element or breakage of the sensor terminalmembers due to application of stress on the sensor terminal membersthemselves or between the sensor terminal members and the sensor elementbecause of positional or postural deviation of the sensor terminalmembers can be prevented from occurring, the separator can be stablyfixed inside the metal outer tube, and the reliability is high.

As described above, at least one of the outer-tube butting portion andthe flange butting portion is required to form the inclined face whichis more radially outward positioned as further advancing toward the tipend. In the case where the outer-tube butting portion forms a taperedface in which the diameter is made larger as further advancing towardthe tip end, for example, the flange butting portion may be a taperedface which butts against the tapered face in a surface or point contactstate, or have another form. In the case where the flange buttingportion forms a tapered face in which the diameter is made larger asfurther advancing toward the tip end, the outer-tube butting portion maybe a tapered face which butts against the tapered face in a surface orpoint contact state, or have another form.

The other solving means is a sensor having: a sensor element; a metalshell which holds the sensor element; one or more sensor terminalmembers which are electrically connected to the sensor element, andwhich elongate from the sensor element toward a rear end; a metal outertube which is connected to the metal shell at a tip end portion of themetal outer tube itself; and an electrically insulative separator whichis housed inside the metal outer tube, in which the sensor terminalmembers are positioned, and which provides at least one of insulationbetween the sensor terminal members, and insulation between the sensorterminal members and the metal outer tube, wherein the separator has: arear end side portion; and a flange portion which is positioned on a tipend side with respect to the rear end side portion, and which is largerin diameter than the rear end side portion, the metal outer tube has astep portion or an inner projection which butts against the flangeportion of the separator, both of an outer-tube butting face of theflange portion of the separator, and a flange butting face of the stepportion or the inner projection of the metal outer tube form an inclinedface which is more radially outward positioned as further advancingtoward the tip end, the outer-tube butting face butting against the stepportion or the inner projection of the metal outer tube and facing therear end side, the flange butting face butting against the outer-tubebutting face of the flange portion of the separator, and the separatoris held by the metal outer tube in a state where the separator ispressed toward the rear end.

In the sensor of the invention, the flange portion of the separator hasthe outer-tube butting face forming an inclined face which faces therear end side, which butts against the step portion or the innerprojection of the metal outer tube, and which is more radially outwardpositioned as further advancing toward the tip end, for example, an atapered face in which the diameter is made larger as further advancingtoward the tip end. Furthermore, also the step portion or the innerprojection of the metal outer tube has the flange butting face formingan inclined face which faces the tip end side, which butts against theouter-tube butting face of the separator, and which is more radiallyoutward positioned as further advancing toward the tip end, for example,a tapered face in which the diameter is made larger as further advancingtoward the tip end. Moreover, the separator is pressed toward the rearend. Namely, the separator is pressed in a direction along which theouter-tube butting face and the flange butting face approach each other.Furthermore, the separator is held inside the metal outer tube in thisstate.

Even in the case where, during a process of assembling the sensor, theaxis of the separator is set to be deviated from that of the metal outertube, when the separator is pressed toward the rear end, the separatormoves along the inclined faces of the separator and the metal outer tubeso as to reduce the deviation between the axes. Therefore, the positionof the separator with respect to the metal outer tube can be adequatelydetermined, and hence also the positions of the sensor terminal membersplaced in the separator can be correctly determined. As a result, in thesensor, a defect such as destruction of the sensor element or breakageof the sensor terminal members due to application of stress on thesensor terminal members themselves or between the sensor terminalmembers and the sensor element because of positional or posturaldeviation of the sensor terminal members can be prevented fromoccurring, the separator can be stably fixed inside the metal outertube, and the reliability is high.

In the sensor described above, it is requested to have one or moresensor terminal members which are electrically connected to the sensorelement. An example of the case of one sensor terminal member is a casewhere one of sensor signals is output through the sensor terminalmember, and the other sensor signal is set as the ground potentialthrough the metal shell and the metal outer tube. In this case,insulation between the sensor terminal member and the metal outer tubeis provided by the separator. An example of the case of plural sensorterminal members is a case where sensor signals of + and − are output.In this case, insulation between the sensor terminal members is providedby the separator.

Any mechanism which can press the separator toward the rear end may beemployed in order to press the separator. For example, an annular metalplate in which nail portions protruding in the form of a gear are formedin the outer periphery is pressingly inserted into the metal outer tube,the nail portions are pressingly contacted with the inner wall of themetal outer tube, and the annular body portion butts against the tip endside face of the flange portion of the separator, whereby the separatorcan be pressed toward the rear end.

As the sensor, any sensor having a sensor element, a metal shell, ametal outer tube, a separator, and the like can be used. For example, agas sensor such as an oxygen sensor, a NOx sensor, or an HC sensor, atemperature sensor, and other sensors can be used.

Preferably, the sensor is configured so that the flange portion of theseparator has a tip end side face facing the tip end side, and thesensor comprises a pressing member which is held inside the metal outertube, and which butts against the tip end side face of the flangeportion to press the separator toward the rear end, the pressing memberbeing in point contact with the tip end side face as seen in a radialdirection.

Depending on the attachment position and manner of the sensor terminalmembers, and also on the arrangement of lead wires connected to thesensor terminal members, the shape of a grommet which is fitted into arear end opening of the metal outer tube in order to make the interiorof the metal outer tube airtight, the manner of a airtight seal such ascaulking of the metal outer tube around the grommet, and the like,various forces act on the separator through the sensor terminal membersand the lead wires during a process of assembling the sensor, and try tochange the posture of the separator.

When the separator is firmly fixed to the metal outer tube, however, theposture of the separator is not changed. Therefore, stresses are appliedto the sensor terminal members, the sensor element, and the lead wires,and there arises the possibility that a defect such as that the sensorterminal members or the lead wires are broken occurs.

By contrast, in the sensor of the invention, the pressing member has,for example, an annular shape, or an annular shape in which variousportions are interrupted, and is in point contact with the tip end sideface as seen in a radial direction. As compared with the case where,although the separator is similarly pressed toward the rear end, thebutting portion has a width and annularly extends, therefore, theposture of the separator (for example, deviation of the axis of theseparator with respect to that of the metal outer tube, inclination ofthe axis, and rotation) is changed in a relatively easy manner during aprocess of assembling the sensor. Consequently, stresses are hardlyapplied to the sensor terminal members, the lead wires, and the likeduring a process of assembling the sensor. As a result, the resultingsensor is a sensor in which a defect such as crack of the sensorelement, or breakage of the sensor terminal members or the lead wirescan be prevented from occurring, and which is highly reliable.

Preferably, any of the above-described sensors is configured as a sensorin which the sensor element is a cylindrical gas sensor element in whicha tip end side is closed, the sensor has: a rod heater which is insertedinto a bottomed hole of the gas sensor element; and one or more heaterterminal members which are electrically connected to the heater, and theseparator is a separator which provides insulation between the sensorterminal members and the heater terminal members.

The sensor of the invention uses a cylindrical gas sensor element inwhich a tip end side is closed, as the sensor element, has a rod heaterwhich is inserted into a bottomed hole of the gas sensor element, andheater terminal members which are electrically connected to the heater,and the separator provides insulation between the sensor terminalmembers, and also insulation between the heater terminal members. In asensor (gas sensor) which has a heater and heater terminal members inaddition to a sensor element as described above, the position of theseparator in the metal outer tube is affected also by the arrangementand posture of the heater terminal members, the heater, etc., and hencethe axis of the separator tends to be set to be deviated from that ofthe metal outer tube during a process of assembling the sensor.

By contrast, in the sensor of the invention, as described above, theflange portion of the separator comprises the outer-tube butting faceforming an inclined face which is more radially outward positioned asfurther advancing toward the tip end, and also the step portion or theinner projection of the metal outer tube has the flange butting faceforming an inclined face which is more radially outward positioned asfurther advancing toward the tip end. Moreover, the separator is pressedtoward the rear end. In the same manner as described above, therefore,the position of the separator with respect to the metal outer tube canbe adequately determined, and hence also the positions of the sensorterminal members and the heater terminal members held by the separatorcan be correctly determined. As a result, in the sensor, a defect suchas destruction of the sensor element, breakage of the sensor terminalmembers, destruction (bending) of the heater, or breakage of the heaterterminal members due to application of stress on the sensor terminalmembers themselves, between the sensor terminal members and the sensorelement, the heater terminal members themselves, or between the heaterterminal members and the heater because of positional or posturaldeviation of the sensor terminal members and the heater terminal memberscan be prevented from occurring, and the reliability is high.

The other solving means is a method of producing a sensor, the sensorhaving: a sensor element; a metal shell which holds the sensor element;one or more sensor terminal members which are electrically connected tothe sensor element, and which elongate from the sensor element toward arear end; a metal outer tube which is connected to the metal shell at atip end portion of the metal outer tube itself; and an electricallyinsulative separator which is housed inside the metal outer tube, theseparator including: a rear end side portion which is positioned on aside of the rear end; a tip end side portion which is positioned on aside of a tip end; and a flange portion which is positioned at a middlebetween the rear end side portion and the tip end side portion, which islarger in diameter than the rear end side portion and the tip end sideportion, and which has a tip end side face facing the tip end sidebetween the flange portion and the tip end side portion, and a rear endside face facing the rear end side between the flange portion and therear end side portion, the sensor terminal members being positionedinside, the separator providing at least one of insulation between thesensor terminal members, and insulation between the sensor terminalmembers and the metal outer tube, the metal outer tube having a stepportion or an inner projection which butts against the rear end side ofthe flange portion of the separator, the sensor having a pressing memberwhich presses the separator toward the rear end, wherein the methodcomprises: a butting step of, in a state where the sensor terminalmembers are positioned inside the separator, the pressing member is heldby an outer periphery of the tip end side portion of the separator, andthe flange portion of the separator and the step portion or the innerprojection of the metal outer tube butt against each other, moving atleast one of the metal outer tube and the metal shell in a directionalong which the metal outer tube and the metal shell approach eachother, thereby causing the tip end portion of the metal outer tube tobutt against the metal shell; and

a deforming step of, in a state where the sensor terminal members arepositioned inside, the flange portion of the separator in which thepressing member is held by the outer periphery of the tip end sideportion, and the step portion or the inner projection of the metal outertube butt against each other, and the pressing member butts against thetip end side face of the flange portion of the separator, radiallyinward pressing a portion of the metal outer tube to form a deformedportion which inward protrudes, the portion being positioned in aradially outer side of the pressing member, and deform also the pressingmember so that the pressing member presses the separator toward the rearend.

In the conventional art described above, in the state where the leadwire 1081 and the like are not passed through the insulating member1005, the insulating member 1005 is attached and fixed to the inside ofthe first metal cover 1003 by using the elastic member 1006. Therefore,the lead wire 1081 and the like must be then passed through theinsulating member 1005 in the state where it is held inside the firstmetal cover 1003, and the lead terminal 1071, the connector 1075, andthe like must be placed inside the insulating member 1005. Consequently,the work is cumbersome, and, when the positions of the lead terminal1071, the connector 1075, and the like are deviated, stresses are easilyapplied to the lead terminal and the like during a process of attachingthe separator.

It may be contemplated that, conversely, the lead wire 1081 is passedthrough the insulating member 1005, the lead terminal 1071, theconnector 1075, and the like are placed inside insulating member 1005,and the insulating member 1005 in this state is then attached to theinside of the first metal cover 1003. In this case, however, theconnector 1075, the lead wire 1081, and the like exist inside theinsulating member 1005, and hence it is difficult to pressingly insertthe elastic member 1006 between the insulating member 1005 and the firstmetal cover 1003.

By contrast, in the method of producing a sensor of the invention, aseparator in which the sensor terminal members are positioned inside theseparator, and the pressing member is attached and held to the tip endside portion is previously prepared. Thereafter, one of the butting stepand the deforming step is first conducted, and the other step is thenconducted.

In the butting step, in the state where the flange portion of theseparator and the step portion or the inner projection of the metalouter tube butt against each other, at least one of the metal outer tubeand the metal shell is moved in a direction along which they approacheach other, thereby causing the tip end portion of the metal outer tubeto butt against the metal shell. By contrast, in the deforming step, inthe state where the flange portion of the separator and the step portionor the inner projection of the metal outer tube butt against each other,the deformed portion is formed, and also the pressing member isdeformed, so that the separator is pressed toward the rear end by thepressing member to cause the flange portion of the separator and thestep portion or the inner projection of the metal outer tube to be inclose contact with each other.

According to the configuration, in the work of placing the sensorterminal members inside the separator, the metal outer tube does notimpede the work, and hence the work can be easily conducted. Unlike theconventional art described above, moreover, it is not required topressingly insert the elastic member into the metal outer tube beforethe tip end portion of the metal outer tube is caused to butt againstthe metal shell. Namely, the fixation of the separator can be conductedeither before or after the metal outer tube is caused to butt againstthe metal shell. Moreover, when the deformed portion is formed from theoutside of the metal outer tube, the separator can be pressed toward therear end. Therefore, the fixation can be easily conducted without beingaffected by the sensor terminal members placed in the separator, and thelike.

Since the tip end portion of the metal outer tube is caused to buttagainst the metal shell, the longitudinal positions of the metal outertube and the separator with respect to the metal shell can bedetermined.

The tip end portion of the metal outer tube and the metal shell whichbutt against each other can be connected to each other by a caulkingprocess or laser welding. Alternatively, the tip end portion of themetal outer tube and the metal shell may be provisionally fixed to eachother by a caulking process, and, after the deforming step and the likeare conducted, they may be connected to each other by laser welding.Alternatively, while the tip end portion of the metal outer tube is keptto be pressed against the metal shell, production steps may proceedwithout conducting provisional fixation and welding, and, after thepressing member is deformed in the deforming step, the tip end portionof the metal outer tube and the metal shell may be connected to eachother by laser welding or the like.

Preferably, the method of producing a sensor is a method of producing asensor in which the rear end side face of the flange portion of theseparator forms an inclined face which is more radially outwardpositioned as further advancing toward the tip end, and the step portionor the inner projection of the metal outer tube has a flange buttingface forming an inclined face which butts against the rear end side faceof the separator, and which is more radially outward positioned asfurther advancing toward the tip end.

In the method of producing a sensor of the invention, the rear end sideface of the flange portion of the separator butts against the flangebutting face of the step portion or the inner projection of the metalouter tube, and both the rear end side face of the flange portion (therear end side face corresponds to the outer-tube butting face) and theflange butting face of the metal outer tube form an inclined face whichis more radially outward positioned as further advancing toward the tipend. In the deforming step, when the separator is pressed toward therear end by the pressing member, therefore, the separator moves alongthe inclined face in a direction along which the axis of the separatorcoincides with that of the metal outer tube, and hence the position ofthe separator with respect to the metal outer tube can be adequatelydetermined. Since the position of the separator with respect to themetal outer tube can be adequately determined, also the position of thesensor terminal members held by the separator can be correctlydetermined. As a result, in the sensor, a defect such as destruction ofthe sensor element or breakage of the sensor terminal members due toapplication of stress on the sensor terminal members themselves orbetween the sensor terminal members and the sensor element because ofpositional or postural deviation of the sensor terminal members can beprevented from occurring, the separator can be stably fixed to theinside of the metal outer tube, and the reliability is high.

Preferably, any one of the methods of producing a sensor is a method ofproducing a sensor in which the pressing member has: a metal tubeportion having an inner diameter which is larger than an outer diameterof the tip end side portion of the separator, and an outer diameterwhich is smaller than an inner diameter of the metal outer tube; and anelastic holding portion which, when the metal tube portion is attachedto the tip end side portion of the separator, elastically butts againstthe tip end side portion of the separator inside the metal tube portion,to hold the metal tube portion to the separator, and, in accordance withthe formation of the deformed portion of the metal outer tube in thedeforming step, the tip end side face of the flange portion of theseparator is pressed toward the rear end by the rear end of the metaltube portion.

In the method of producing a sensor of the invention, the pressingmember of a simple structure having the metal tube portion and theelastic holding portion is used. The pressing member can be easilyattached to the tip end side portion of the separator, and can beeconomically produced. When the deformed portion is formed in the metalouter tube, moreover, a portion of the metal tube portion which is onthe side of the rear end with respect to a portion that is deformed inaccordance with the formation moves slightly toward the rear end.Therefore, the rear end of the metal tube portion presses and pressesthe tip end side face of the flange portion of the separator toward therear end. In other words, in the tip end side face of the flange portionof the separator, the butting portion with respect to the pressingmember exists in an annular form, and they are in point contact witheach other as seen in a radial direction. As compared with the casewhere, although the separator is similarly pressed toward the rear end,the butting portion has a width and annularly extends, therefore, theposture of the separator (for example, deviation of the axis of theseparator with respect to that of the metal outer tube, inclination ofthe axis, and rotation) can be changed in a relatively easy mannerduring a process of assembling the sensor. Consequently, the posture ofthe separator is changed during a process of assembling the sensor, sothat stresses are hardly applied to the sensor terminal members, thelead wires, and the like. As a result, the resulting sensor is a sensorin which a defect such as breakage of the sensor terminal members or thelead wires can be prevented from occurring, and which is highlyreliable.

Preferably, the method of producing a sensor is a method of producing asensor in which the elastic holding portion of the pressing member isformed in three or more places which are arranged at regular intervalsin a circumferential direction of the metal tube portion.

Since the elastic holding portion of the pressing member is formed inthree or more places which are arranged at regular intervals in acircumferential direction, the tip end side face of the flange portionof the separator can be adequately pressed toward the rear end.

Preferably, the method of producing a sensor is a method of producing asensor in which the metal tube portion of the pressing member has a rearend portion which is curved inward or outward in a radial direction.

The rear end of the metal tube portion butts against the tip end sideface of the flange portion of the separator. When the posture of theseparator is to be changed, therefore, friction is produced between thetip end side face of the separator and the end face of the rear end ofthe metal tube portion, to try to impede the posture change of theseparator. In the invention, the rear end portion of the metal tubeportion has the inward or outward curved shape, and hence the tip endface of the separator butts against the curved rear end portion.Therefore, friction with respect to the tip end side face of theseparator can be reduced, so that the posture change of the separatorcan be conducted more easily.

Preferably, any one of the methods of producing a sensor is a method ofproducing a sensor in which the elastic holding portion of the pressingmember is a J-shaped elastic holding portion which is positioned in therear end of the metal tube portion, which elongates radially inward, andwhich is gradually changed in direction to elongate toward the tip endto be curved into a substantially J-like shape.

In the method of producing a sensor of the invention, the pressingmember in which the elastic holding portion is a J-shaped elasticholding portion having a substantially J-like shape is used. When theelastic holding portion is a J-shaped elastic holding portion, a moreadequate elasticity can be easily obtained by adjusting the radius,width, or the like of the curved portion.

Preferably, any one of the methods of producing a sensor is a method ofproducing a sensor in which, in a state where the outer-tube buttingface of the separator and the flange butting face of the metal outertube butt against each other, the flange portion of the separator issmaller in diameter than a portion of the metal outer tube surroundingthe flange portion, and a portion of the metal tube portion of thepressing member, the portion being positioned on the side of the rearend with respect to the deformed portion of the metal tube portion whichis formed in the deforming step, is smaller in diameter than a portionof the metal outer tube surrounding the portion, and larger in diameterthan the flange portion.

According to the methods of producing a sensor, even in the case where astone or the like hits the peripheral portion of the flange portion ofthe metal outer tube or a portion between it and the deformed portionand the metal outer tube is largely depressed, a part of the metal tubeportion which is large in diameter than the flange portion bumps againstthe metal outer tube before the depressed metal outer tube bumps againstthe flange portion, thereby absorbing the shock. Therefore, breakagesuch as that in which the depressed metal outer tube violently collideswith the flange portion and the separator including the flange portioncracks can be prevented from occurring.

Preferably, the method of producing a sensor is a method of producing asensor in which the pressing member is a cylindrical rubber memberhaving an inner diameter which is smaller than an outer diameter of thetip end side portion of the separator, and an outer diameter which, whenthe member is attached to the tip end side portion of the separator, issmaller than an inner diameter of the metal outer tube, and, inaccordance with the formation of the deformed portion of the metal outertube in the deforming step, is deformed to press the tip end side faceof the flange portion of the separator toward the rear end.

In the method of producing a sensor, since a cylindrical rubber memberis used as the pressing member, the handling is facilitated.

Preferably, any one of the methods of producing a sensor is a method ofproducing a sensor in which the sensor element is a cylindrical gassensor element in which a tip end side is closed, the sensor has: a rodheater which is inserted into a bottomed hole of the gas sensor element;and one or more heater terminal members which are electrically connectedto the heater, the separator holds insulation between the sensorterminal members and the heater terminal members, the butting step isconducted in a manner that, in a state where the separator is looselyinserted into the metal outer tube, at least one of the metal outer tubeand the metal shell is moved in a direction along which they approacheach other, to cause the tip end portion of the metal outer tube to buttagainst the metal shell, and the heater is inserted into the gas sensorelement held by the metal shell, and the deforming step is conductedafter the butting step.

In the method of producing a sensor of the invention, a cylindrical gassensor element in which a tip end side is closed is used as the sensorelement, the sensor element comprises a heater, and, in the buttingstep, the tip end portion of the metal outer tube is caused to buttagainst the metal shell, and moreover the heater is inserted into thegas sensor element.

If the deforming step is conducted in advance of the butting step, theseparator is fixed to the metal outer tube. In the case where the heateris inserted into the bottomed hole of the gas sensor element with beinglargely inclined because of deviation of the placement of heaterconnecting terminals in the separator or the like, therefore, stressesare applied to the heater, and a defect such as that the heater is bent,or that portions connecting the heater with the heater connectingterminals are broken may occur.

By contrast, in the production method of the invention, the heater isinserted into the gas sensor element in the butting step, and thedeforming step is then conducted. In the butting step, the separator isloosely inserted into the metal outer tube. When stresses are applied tothe heater, the heater terminal members, and the like in accordance withthe insertion of the heater, therefore, the position of the separator,the inclination of the axis, and the like are adjusted so as to reducethe stresses. Thereafter, the separator is fixed to the metal outer tubewith being pressed by the pressing member in the deforming step.Consequently, the resulting sensor is a sensor (gas sensor) in whichsmaller stresses are applied to the heater and the heater terminalmembers, and a defect such as that the heater is bent or broken hardlyoccurs, and which is highly reliable. An example of the heater is a rodheater having a circular section shape or a rectangular section shape.

Preferably, the method of producing a sensor is a method of producing asensor in which the butting step includes an inserting and positioningstep of positioning and inserting a tip end of the heater to be guidedinto a rear end opening of the gas sensor element, the tip end furtherprotruding toward the tip end than the tip end portion of the metalouter tube.

In the method of producing a sensor of the invention, the butting stepincludes the inserting and positioning step, and the tip end of theheater is guided into the rear end opening of the gas sensor element.Therefore, the heater can be easily inserted, and it is possible toeliminate a defect such as that the tip end of the heater butts againsta rear end portion of the gas sensor element and the heater is bent.

Preferably, the method of producing a sensor is a method of producing asensor in which the inserting and positioning step is conducted bygripping a part of a portion of the heater which further protrudestoward the tip end than the tip end portion of the metal outer tube, bya chuck device, and adjusting a position of the tip end of the heater.

In the method of producing a sensor, in the inserting and positioningstep, the tip end of the heater is guided by the chuck device, and hencethe tip end of the heater can be inserted easily and surely into therear end opening of the gas sensor element.

The further solving means is an assembly of a separator and a pressingmember which is to be used in a sensor, the sensor having: a sensorelement; a metal shell which holds the sensor element; one or moresensor terminal members which are electrically connected to the sensorelement, and which elongate from the sensor element toward a rear end; ametal outer tube which is connected to the metal shell at a tip endportion of the metal outer tube itself; and an electrically insulativeseparator which is housed inside the metal outer tube, the separatorincluding: a rear end side portion which is positioned on a side of therear end; a tip end side portion which is positioned on a side of a tipend; and a flange portion which is positioned at a middle between therear end side portion and the tip end side portion, which is larger indiameter than the rear end side portion and the tip end side portion,and which has a tip end side face facing the tip end side between theflange portion and the tip end side portion, and an outer-tube buttingface facing the rear end side between the flange portion and the rearend side portion, the sensor terminal members being positioned inside,the separator providing at least one of insulation between the sensorterminal members, and insulation between the sensor terminal members andthe metal outer tube, the metal outer tube having a step portion or aninner projection which has a flange butting face butting against theouter-tube butting face of the flange portion of the separator, thesensor having a pressing member which presses the separator toward therear end, wherein the pressing member has: a metal tube portion havingan inner diameter which is larger than an outer diameter of the tip endside portion of the separator, and an outer diameter which is smallerthan an inner diameter of the metal outer tube; and an elastic holdingportion which is placed inside the metal tube portion, the elasticholding portion elastically butts against the tip end side portion ofthe separator, and the pressing member is held by the separator.

In the assembly of the invention, the pressing member is held by theseparator by means of the elastic force of itself. When the assembly isused in production of a sensor, therefore, less labor is required, andthe sensor can be more economically produced as compared with the casewhere the separator and the pressing member are separately attached.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing the whole configuration of a gassensor of the conventional art.

FIG. 2 is an explanatory view showing the whole configuration of a gassensor of an embodiment.

FIG. 3( a) is a side view of a separator, (b) is a plan view, (c) is abottom view, (d) is a section view taken along A—A, and (e) is a sectionview taken along B—B.

FIG. 4 is an exploded perspective view showing a state of attaching anoxygen sensor element and a heater to the separator.

FIG. 5 is a partially cutaway side view of a metal outer tube.

FIG. 6 is a partially cutaway side view of a pressing metal part.

FIG. 7 is an explanatory view showing a state where a separator in whichsensor terminal metal parts and the like are held is placed in the metalouter tube.

FIG. 8 is an explanatory view showing a manner of guiding and insertingthe heater into a rear end opening of an oxygen sensor element.

FIG. 9 is an explanatory view comparatively showing a case where anouter-tube butting face of a flange portion of the separator and aflange butting face of an inner projection of the metal outer tube arenot tapered (a), and a case where they are tapered (b).

FIG. 10 is an explanatory view showing a manner of caulking the metalouter tube and a metal shell to provisionally connect them.

FIG. 11 is an explanatory view showing a deforming step of pressing themetal outer tube from the outer periphery to form a deformed portion,and deforming also the pressing metal part.

FIG. 12 is a partial enlarged view showing a manner of deforming themetal outer tube and the pressing metal part in the deforming step, (a)shows a state before deformation, and (b) shows a state afterdeformation.

FIG. 13 is an explanatory view showing a manner of caulking a grommet.

FIG. 14 is an explanatory view showing a manner of laser-welding themetal outer tube and the metal shell.

The reference numerals in the figures are as follows:

-   1 oxygen sensor (gas sensor, sensor)-   2 oxygen sensor element (gas sensor element, sensor element)-   2 a bottomed hole-   2 b sensor external electrode layer-   2 c sensor internal electrode layer-   2 h rear end opening-   3 metal shell-   3 d connecting portion-   11 first sensor terminal metal part (sensor terminal member)-   12 second sensor terminal metal part (sensor terminal member)-   13, 14 sensor output lead wire-   15 heater-   15 d rear end face-   16, 17 heater terminal metal part (heater terminal member)-   18, 19 heater lead wire-   21 metal outer tube-   22 a tip end portion-   24 inner projection-   24 b flange butting face-   31 separator-   33 tip end side portion-   34 flange portion-   34 a outer-tube butting face-   34 b tip end side face-   39 assembly (assembly of separator and pressing member)-   41 pressing metal part (pressing member)-   42 metal tube portion-   42 b rear end portion (of metal tube portion)-   43 J-shaped elastic holding portion-   43 a butting portion-   CH chuck mechanism

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be described with reference to FIGS.2 to 14. FIG. 2 is an explanatory view showing the whole configurationof an oxygen sensor 1 of the embodiment. The oxygen sensor 1 comprises ahollow shaft-like oxygen sensor element 2 in which the tip end isclosed, and a heater 15 which is inserted into a bottomed hole 2 a ofthe oxygen sensor element 2. The oxygen sensor element 2 is formed intoa hollow shaft-like shape by a solid electrolyte having an oxygen ionconductivity.

A typical example of such a solid electrolyte is ZrO2 into which Y2O3 orCaO is solid-dissolved. A solid solution of an oxide of another alkalineearth metal or rear earth metal and ZrO2 may be used. Furthermore, ZrO2serving as a basic component may contain HfO2.

On the inner face of the bottomed hole 2 a of the oxygen sensor element2, a sensor internal electrode layer 2 c which is formed as a porousmember by, for example, Pt or a Pt alloy is formed so as to cover asubstantially whole of the inner face. On the other hand, a sensorexternal electrode layer 2 b of a similar porous member is disposed on atip end portion of the outer face of the oxygen sensor element 2 (seeFIG. 4). An engagement flange portion 2 s which radially outwardprotrudes is disposed in an axially middle portion of the oxygen sensorelement 2. The engagement flange portion 2 s is engaged and held byinsulators 5, 7 made of insulative ceramic, and ceramic powder 6 formedby talc, whereby the oxygen sensor element 2 is airtightly held by acylindrical metal shell 3 which has a passage hole at the center. Theoxygen sensor element 2 is passed through the passage hole. In thisdescription, among the directions along the axis of the oxygen sensorelement 2 (the vertical directions in FIG. 2), the side directed towardthe tip end portion (the closed side, the lower portion in FIG. 2) isreferred to as “tip end side”, and the side directed in the oppositedirection (the upper portion in FIG. 2) is referred to as “rear endside”.

The metal shell 3 has a threaded portion 3 b and a hexagonal portion 3 cwhich are used for attaching the oxygen sensor 1 to an attachmentportion of an exhaust pipe or the like. A protector 4 is connected to aprotector connecting portion 3 a by laser welding. The protector 4 isattached so as to cover a tip end portion of the oxygen sensor element 2which protrudes from a tip end opening of the metal shell 3. The oxygensensor 1 is used while a portion which is on the side of the tip endwith respect to the threaded portion 3 b is positioned in an engine suchas an exhaust pipe, and a portion which is on the side of the rear endis positioned in the outside or the atmosphere. A plurality of gaspassage ports through which exhaust gas can be passed are formed in theprotector 4.

By contrast, a rear end portion 3 e of the metal shell 3 is airtightlyheld with being caulked with the insulator 7 via a ring packing 9. A tipend portion 22 a of a cylindrical metal outer tube 21 is secured to aconnecting portion 3 d on the rear end side of the hexagonal portion 3 cby laser welding from the outside. A grommet 51 made of rubber and thelike is fitted into a rear end opening of the metal outer tube 21, andthen subjected to caulking to attain sealing. A filter member 52 whichintroduces the atmosphere into the metal outer tube 21, and whichprevents water from entering is placed in a center portion of thegrommet 51. A separator 31 made of insulative alumina ceramic isdisposed on the tip end side of the grommet 51. Sensor output lead wires13, 14 and heater lead wires 18, 19 are placed so as to pass through theseparator 31 and the grommet 51 (see FIGS. 2 and 4).

As shown in a side view (see FIG. 3( a)), the separator 31 shown in FIG.3 has a rear end side portion 32, a tip end side portion 33, and aflange portion 34 which is positioned between them, and which is largerin diameter than them. In the flange portion 34, an outer-tube buttingface 34 a in which the diameter is made larger as further advancingtoward the tip end side (the lower portion in FIG. 2) to form a taperedface is formed between the flange portion and the rear end side portion32. By contrast, a tip end side face 34 b which forms a stepwise leveldifference is formed between the flange portion and the tip end sideportion 33. As shown in FIGS. 3( b), (c), lead wire passage holes 31 a,31 b through which the lead wires 13, 14, 18, 19 are to be passed areformed so as to axially pass through the separator 31. In an end face onthe rear end side, an air vent channel 31 c is formed at a positionwhere the channel does not interfere with the four lead wire passageholes 31 a, 31 b, in a cross pattern and in a direction perpendicular tothe axis. A bottomed holding hole 31 d which is opened in the tip endface of the separator 31 is formed in the axial direction.

As shown in FIGS. 2 and 4, the lead wires 13, 14, 18, 19 are passedthrough the holding hole 31 d and the lead wire insertion holes 31 a, 31b, and connector portions 11 a, 12 a of first and second sensor terminalmetal parts 11, 12, and heater terminal metal parts 16, 17 are heldinside the separator 31 while being insulated from one another.

As shown in FIG. 3( d), the bottom face 31 e of the holding hole 31 d ispositioned in an axially middle portion of the separator 31. A rear endportion 15 c of the heater 15 is inserted into the holding hole 31 dfrom the axial tip end side of the separator 31, and the rear end face15 d of the heater 15 butts against the bottom face 31 e of the holdinghole 31 d, whereby the heater 15 is positioned in the axial directionwith respect to the separator 31.

As shown in FIG. 4, the first sensor terminal metal part 11 has theconnector portion 11 a, a separator butting portion 11 b, and aninsertion portion 11 c which are integrally molded. Among thecomponents, the connector portion 11 a grips a core wire of the sensoroutput lead wire 13 to electrically connect the first sensor terminalmetal part 11 and the sensor output lead wire 13. The separator buttingportion 11 b elastically butts against the holding hole 31 d of theseparator 31 (see FIG. 2) to hold the first sensor terminal metal part11 in the separator 31. The insertion portion 11 c is inserted into thebottomed hole 2 a of the oxygen sensor element 2 to be electricallyconnected to the sensor internal electrode layer 2 c. The insertionportion 11 c includes a lower pressing portion 11 d and an upperpressing portion 11 e. When the insertion portion 11 c is inserted intothe bottomed hole 2 a of the oxygen sensor element 2, the insertionportion 11 c presses the heater 15 surrounded thereby, to cause the axisof the heater 15 to deviate from the center axis of the oxygen sensorelement 2, whereby the posture of the heater 15 is adjusted so that aheating portion 15 a is in contact with the inner wall (the sensorinternal electrode layer 2 c) of the bottomed hole 2 a of the oxygensensor element 2. A flange portion 11 g is disposed in the rear end sideof the insertion portion 11 c in order to prevent the insertion portion11 c from entering the bottomed hole 2 a of the oxygen sensor element 2.

When the heating portion 15 a formed in the heater is made eccentric tobe in contact with the inner wall of the bottomed hole 2 a of the oxygensensor element 2, the thermal energy is concentrated into a smallervolume. This is effective in shortening the activation time of theoxygen sensor 1.

On the other hand, the second sensor terminal metal part 12 has theconnector portion 12 a, a separator butting portion 12 b, and a grippingportion 12 c which are integrally molded. Among the components, theconnector portion 12 a grips a core wire of the sensor output lead wire14 to electrically connect the second sensor terminal metal part 12 andthe sensor output lead wire 14. The separator butting portion 12 belastically butts against the holding hole 31 d of the separator 31 (seeFIG. 2) to hold the second sensor terminal metal part 12 in theseparator 31. The gripping portion 12 c grips the outer periphery of thevicinity of rear end of the oxygen sensor element 2.

As shown in FIG. 4, the oxygen sensor element 2 has a connecting layer 2f which is formed in a rear end portion, and which is electricallyconnected to the sensor external electrode layer 2 b via a leading layer2 d. The gripping portion 12 c is electrically connected to theconnecting layer 2 f to be electrically connected also to the sensorexternal electrode layer 2 b. A flange portion 12 f is disposed in thetip end side of the gripping portion 12 c in order to allow the rear endportion of the oxygen sensor element 2 to be easily inserted into thegripping portion 12 c. The leading layer 2 d and the connecting layer 2f are formed by baking.

As shown in FIGS. 2 and 4, the heater 15 is a rod ceramic heater, andthe heating portion 15 a having a resistance heating element (not shown)is formed on a core member which is mainly made of alumina. When theheater 15 is energized through the heater terminal metal parts 16, 17which are brazed to electrode pads 15 e, 15 f, and the heater lead wires18, 19, the tip end portion of the oxygen sensor element 2 is heated.The heater terminal metal part 17 has a connector portion 17 a whichgrips a core wire of the heater lead wire 18 to electrically connect theheater terminal metal part 17 and the heater lead wire 18. Although notshown in FIG. 4, the heater terminal metal part 16 similarly has aconnector portion which grips a core wire of the heater lead wire 19.

The metal outer tube 21 (see FIG. 5) has: a first outer tube potion 22which is made of a metal, which is formed into a substantiallycylindrical shape, which is positioned on the side of the tip end (thelower side in the figure), and in which the tip end portion 22 a on thetip end side is joined to the metal shell 3 as described above; and asecond outer tube potion 23 which is positioned on the rear end sidewith respect to the first outer tube potion, and which is smaller indiameter than the first outer tube potion. In an axially middle portionof the second outer tube potion 23, an inner projection (firstreduced-diameter portion) 24 in which a projection top face 24 aprotrudes in a rectangular shape toward the radially inner side isformed in four places equally arranged in a circumferential direction.In each of the inner projections 24, a flange butting face 24 b formingan inclined face is formed on the tip end side with respect to theprojection top face 24 a. As shown in FIG. 2, the flange butting face 24b butts against the outer-tube butting face 34 a of the separator 31.

As shown in FIG. 2, a pressing metal part 41 is attached to theperiphery of the tip end side portion 33 of the separator 31. As shownin FIG. 6, the pressing metal part 41 has a cylindrical metal tubeportion 42, and also J-shaped elastic holding portions 43 and tubeelongating portions 44 which are formed in a rear end portion 42 a ofthe metal tube portion 42 and integrally with the metal tube portion 42.The J-shaped elastic holding portions 43 are scattered in four placesarranged at regular intervals in a circumferential direction, andelongate toward the radially inner side, and their direction isgradually changed so that the portions elongate toward the tip end sideto be curved into a substantially J-like shape. When the pressing metalpart 41 is attached to the tip end side portion 33 of the separator 31,the J-shaped elastic holding portions 43 are elastically deformed tohold the pressing metal part 41 to the tip end side portion 33 (see FIG.7). The holding strength can be adjusted by the width and shape of theJ-shaped elastic holding portions 43, and the like. The tube elongatingportions 44 are formed between the J-shaped elastic holding portions 43,and inward curved into a J-like shape in the same manner as the J-shapedelastic holding portions 43. However, their curvatures are adjusted sothat the J-shaped elastic holding portions 43 protrude further radiallyinward than the tube elongating portions 44. In accordance withformation of a deformed portion (second reduced-diameter portion) in thesecond outer tube potion 23 of the metal outer tube 21, a deformedportion 42 a is formed also in the metal tube portion 42 as describedlater, so that the metal tube portion 42 presses the tip end side face34 b of the separator 31, and hence the separator 31 toward the rearend. Since the curved tube elongating portions 44 and the J-shapedelastic holding portions 43 are disposed in the rear end portion 42 a ofthe metal tube portion 42 in this way, the posture of the separator 31is hardly prevented from being changed when the metal tube portion buttsagainst the tip end side face 34 b of the separator 31 during a processof producing the oxygen sensor 1 as described later.

The oxygen sensor 1 is produced in the following manner. The sensoroutput lead wires 13, 14 are previously connected to the connectorportions 11 a, 12 a of the first and second sensor terminal metal parts11, 12, respectively. The heater lead wires 18, 19 are previouslyconnected to the connector portion 17 a and the like of the heaterterminal metal parts 16, 17. As shown in the right lower portion of FIG.4, in the state where the heater 15 is positioned inside the insertionportion 11 c of the first sensor terminal metal part 11, the lead wires13, 14, 18, 19 are passed through the holding hole 31 d and the leadwire passage holes 31 a, 31 b of the separator 31. As shown in FIG. 7, apart of the first and second sensor terminal metal parts 11, 12, thewhole of the heater terminal metal parts 16, 17, and the rear endportion 15 c of the heater 15 are then set to a state where they areheld inside the holding hole 31 d with being insulated from one another.As shown in FIG. 9( b), the pressing metal part 41 is attached to theouter periphery of the tip end side portion 33 of the separator 31 toconstitute an assembly 39 (see FIG. 7) in such a manner that a buttingportion 43 a of the J-shaped elastic holding portion 43 (a rear endportion 42 b of the metal tube portion 42) butts against the tip endside face 34 b of the flange portion 34. In the embodiment, theseparator 31 and the pressing metal part 41 are previously set as theassembly 39 so as to be integrally handled, and hence the separator 31and the pressing metal part 41 can be easily handled in steps which aredescribed below.

The left lower portion of FIG. 4 shows a state where the oxygen sensorelement 2 and the second sensor terminal metal part 12 are connected toeach other. However, the oxygen sensor element 2 and the second sensorterminal metal part 12 are connected to each other in the mannerdescribed later, and, in this stage, the second sensor terminal metalpart 12 is not connected to the oxygen sensor element 2.

In this way, the separator 31 in which the lead wire 13 and the like arepassed through, and which holds the first sensor terminal metal part 11and the like is loosely inserted into the metal outer tube 21, and thelead wire 13 and the like are passed through the grommet 51.

As shown in FIG. 8, previously, the oxygen sensor element 2 is securedto the metal shell 3, and the protector 4 is welded to the metal shell3.

The positions of the oxygen sensor element 2 and the metal outer tube 21are adjusted so that their axes coincide with each other, and a buttingstep is conducted as follows. The metal outer tube 21 is moved towardthe tip end (the lower portion in the figure) to attain a state wherethe outer-tube butting face 34 a of the separator 31 and the flangebutting face 24 b of the metal outer tube 21 butt against each other andthe separator 31 is loosely inserted into the metal outer tube 21. Thegrommet 51 is fitted into the rear end portion of the metal outer tube21. Furthermore, the metal outer tube 21 is moved toward the tip end(the lower portion in the figure). The heater 15 is then inserted intothe bottomed hole 2 a of the oxygen sensor element 2, and the metalouter tube 21 is moved toward the tip end until the tip end portion 22 aof the metal outer tube 21 butts against the hexagonal portion 3 c ofthe metal shell 3. The oxygen sensor element 2 and the metal shell 3,the metal outer tube 21 and the heater 15, and the separator 31 arerequested only to be moved so as to relatively approach one another. Incontrast to the above, the oxygen sensor element 2 and the metal shell 3may be moved toward the rear end (the upper portion in the figure).

As a result, also the insertion portion 11 c of the first sensorterminal metal part 11 is inserted together with the heater 15 into thebottomed hole 2 a of the oxygen sensor element 2, to be electricallyconnected to the sensor internal electrode layer 2 c. As a result of theinsertion of the insertion portion 11 c into the bottomed hole 2 a ofthe oxygen sensor element 2, the axis of the heater 15 is inclined anddeviated with respect to that of the oxygen sensor element 2, oradjusted so that the heating portion 15 a of the heater 15 is in contactwith the inner wall of the bottomed hole 2 a. Moreover, the grippingportion 12 c of the second sensor terminal metal part 12 grips the rearend portion of the oxygen sensor element 2 to be electrically connectedto the connecting layer 2 f.

In the embodiment, particularly, the heater 15 is inserted into thebottomed hole 2 a of the oxygen sensor element 2, by pushing the rearend face 15 d of the heater 15 with the bottom face 31 e of the holdinghole 31 d of the separator 31. The separator 31 is moved with beingpushed by the metal outer tube 21. When the metal outer tube 21 is movedtoward the tip end until the tip end portion 22 a of the metal outertube 21 butts against the hexagonal portion 3 c of the metal shell 3,therefore, the depth of the insertion of the heater 15 into the bottomedhole 2 a of the oxygen sensor element 2 can be uniquely determined bythe dimensions of the metal outer tube 21, the separator 31, and theheater 15, and hence it is not required to adjust the insertion depth.

Since the outer-tube butting face 34 a is disposed in the separator 31,and the flange butting face 24 b is disposed in the metal outer tube 21,the following advantages are attained in the butting step. This will bedescribed with reference to FIG. 9.

FIG. 9( a) is an explanatory view comparatively showing a case where,unlike the embodiment, a tapered face is not disposed in a flangeportion SPT of a separator SP, a step-like rear end side face SPTa isformed, and a step-like tip end side face GTDa is disposed also in astep portion GTD of a metal outer tube GT. Although lead wires and aheater are held in the separator SP, they are not shown in the figure.

The outer diameter of the flange portion SPT of the separator SP issmaller than the inner diameter of the metal outer tube. Therefore, theseparator SP is allowed to be placed so that the axis SPx is deviatedfrom the axis GTx of the metal outer tube GT. Even when, in this state,the metal outer tube GT is moved toward the tip end (the lower portionin the figure) and the heater which is not shown is inserted into anoxygen sensor element, no force which causes their axes GTx and SPx tocoincide with each other acts. On the contrary, the movement of theseparator SP is blocked by friction between the rear end side face SPTaof the separator SP and the tip end side face GTDa of the metal outertube GT. While the axis SPx of the separator SP is deviated from theaxis GTx of the metal outer tube GT, and hence the axis SPx of theseparator SP is deviated also from the axis of the oxygen sensorelement, therefore, the heater is inserted into the bottomed hole of theoxygen sensor element. Consequently, when the heater and the firstsensor terminal metal part are inserted into the bottomed hole of theoxygen sensor element and the second sensor terminal metal part gripsthe oxygen sensor element, an oxygen sensor is produced in the statewhere stresses are generated among the heater, the first and secondsensor terminal metal parts, the heater terminal metal parts, and theseparator by the positional deviation of the separator SP. In an extremecase, therefore, there is the possibility that the stresses may causedefects such as that the terminal metal parts are ruptured, that theoxygen sensor element is broken, that the heater is bent, and thatbrazed portions between the heater and the heater terminal metal partsare damaged.

By contrast, in the embodiment shown in FIG. 9( b), the outer-tubebutting face 34 a forming an inclined face is disposed in the separator31, and the flange butting face 24 b forming an inclined face isdisposed in the metal outer tube 21. When the metal outer tube 21 ismoved toward the tip end (the lower portion in the figure) and theheater 15 and the insertion portion 11 c of the first sensor terminalmetal part 11 are inserted into the bottomed hole 2 a of the oxygensensor element 2 or the oxygen sensor element 2 is inserted to thegripping portion 12 c of the second sensor terminal metal part 12, thefriction resistance produced between them causes the outer-tube buttingface 34 a of the separator 31 to be pressed against the flange buttingface 24 b of the metal outer tube 21. Then, the separator 31 is moved sothat the axis 31 x of the separator 31 coincides with the axis 21 x ofthe metal outer tube 21. Therefore, a phenomenon such as described abovein which stresses due to positional deviation of the separator aregenerated in the heater 15, the first and second sensor terminal metalparts 11, 12, and the heater terminal metal parts 16, 17 is eliminatedor reduced. As a result, the terminal metal parts, the heater, and theoxygen sensor element can be prevented from being broken or damaged, andthe resulting oxygen sensor 1 is highly reliable.

In the above-described conventional art, the insulating member 1005 isfixed to the first metal cover 1003 by the elastic member 1006 (see FIG.1). Unlike this, in the butting step in which the heater 15 is insertedinto the oxygen sensor element 2, the separator 31 is not fixed to themetal outer tube 21, but in a loosely inserted state. In the case wherethe heater 15 and the first sensor terminal metal part 11 are insertedinto the bottomed hole 2 a of the oxygen sensor element 2 and the oxygensensor element 2 is gripped by the second sensor terminal metal part 12,even when friction resistances are applied to these members and thentransmitted to the separator 31, therefore, the separator 31 can beadequately moved in the form of inclination or the like. Consequently,stresses are hardly generated between the heater 15 and the terminalmetal parts 11, 12, 16, 17, and the separator 31. Because of this also,the heater and the terminal metal parts can be prevented from beingdamaged.

Preferably, the butting step may include an inserting and positioningstep in which, in an initial stage of the butting step, a chuckmechanism CH grips a portion of the heater 15 protruding from the metalouter tube 21 as shown in FIG. 8, and the position of the tip end 15 bis adjusted so that the tip end can be guided to be inserted into a rearend opening 2 h of the oxygen sensor element 2.

According to the configuration, even when the position of the tip end 15b of the heater 15 is deviated from a predetermined one because of thedimensional tolerance or bending of the heater terminal metal parts 16,17, the heater 15 can be surely inserted into the bottomed hole 2 a.After the tip end 15 b of the heater 15 can be inserted into the rearend opening 2 h, the chuck mechanism CH is released.

Thereafter, as shown in FIG. 10, a connecting portion 3 e of the metalshell 3, and the tip end portion 22 a of the metal outer tube 21 whichis positioned on the outer peripheral side are caulked by a caulking jigCL1 to be provisionally connected, while pressing the metal outer tube21 toward the tip end.

As shown in FIGS. 11 and 12, in the deforming step, the metal outer tube21 is deformed by using a pressing jig PU, and also the pressing metalpart 41 which is positioned inside the metal outer tube is deformed,whereby the separator 31 is fixed to the inside of the metal outer tube21. FIG. 12( a) shows states of the metal outer tube 21, the separator31, and the pressing metal part 41 before deformation. As describedabove, in this state, the outer-tube butting face 34 a forming thetapered face in the flange portion 34 of the separator 31, and theflange butting face 24 b forming the inclined face in the innerprojection 24 of the metal outer tube 21 butt against each other, andthe butting portions 43 a of the J-shaped elastic holding portions 43 ofthe pressing metal part 41 (the rear end portion 42 b of the metal tubeportion 42) butt against the tip end side face 34 b of the flangeportion 34.

In the deforming step, therefore, a part of a pressing metal partsurrounding portion 23 a in the second outer tube potion 23 of the metalouter tube 21 which is positioned outside the pressing metal part 41 isdeformed. Specifically, a part of the pressing metal part surroundingportion 23 a is pressed by using a pressing jig PU so as to reduce thediameter, whereby the deformed portion 23 b is formed into an annularshape as shown in FIG. 12( b). In accordance with this, also a part ofthe metal tube portion 42 of the pressing metal part 41 is deformed soas to reduce the diameter, and a deformed portion 42 a is formed. As aresult, the deformed portion 23 b of the metal outer tube 21 and thedeformed portion 42 a of the pressing metal part 41 are in close contactwith each other, and the pressing metal part 41 is held and fixed to themetal outer tube 21.

When the deformed portion 42 a is formed in the pressing metal part 41in this way, the portion of the metal tube portion 42 which is on theside of the rear end (the upper portion in the figure) with respect tothe deformed portion 42 a is slightly moved toward the rear end.Therefore, the curved rear end portion 42 b of the metal tube portion 42presses the flange portion 34 of the separator 31 toward the rear end(the upper portion in the figure). As a result, the flange portion 34 issandwiched between the metal tube portion and the flange butting face 24b, and the separator 31 is fixed to the metal outer tube 21. Moreover,the outer-tube butting face 34 a of the flange portion 34 is pressed soas to be pressed against the flange butting face 24 b of the metal outertube 21. Even when the axis 31 x of the separator 31 is deviated fromthe axis 21 x of the metal outer tube 21 for any reason, therefore, thedeforming step causes the separator 31 to be moved and fixed so that theaxis 31 x of the separator 31 coincides with the axis 21 x of the metalouter tube 21.

Particularly, the pressing metal part 41 comprises the J-shaped elasticholding portions 43 and tube elongating portions 44. Therefore, thebutting portion between the tip end side face 34 b and the pressingmetal part 41 (the J-shaped elastic holding portions 43 and tubeelongating portions 44) is formed into an interrupted annular shape of avery small width. As compared with the case where such a butting portionextends into a wide annular shape, therefore, the butting portion haswidth and annularly extends, therefore, the posture of the separator 31(for example, deviation of the axis 31 x of the separator 31 withrespect to the axis 21 x of the metal outer tube 21, inclination of theaxis 31 x, and rotation) can be changed in a relatively easy manner.

Therefore, a phenomenon in which stresses due to positional deviation ofthe separator 31 are generated in the heater 15, the first and secondsensor terminal metal parts 11, 12, and the heater terminal metal parts16, 17 is eliminated or reduced also by the deforming step. As a result,the terminal metal parts and the heater can be prevented from beingbroken or damaged, and the resulting oxygen sensor 1 is highly reliable.

In the embodiment, the pressing metal part 41 is used. After the heater15 is inserted into the bottomed hole 2 a of the oxygen sensor element2, the oxygen sensor element 2 and the first and second sensor terminalmetal parts 11, 12 are electrically connected, and the metal outer tube21 butts against the metal shell 3, therefore, the metal outer tube 21is deformed to fix the separator 21.

In the case where the deforming step is first conducted and the buttingstep is then conducted, the butting step is conducted in the state wherethe separator 31 is already fixed to the metal outer tube 21. In thebutting step, even when stresses are applied to the first and secondsensor terminal metal parts 11, 12, the heater terminal metal parts 16,17, the heater 15, and the like because of displacement deviation ordeformation of the first and second sensor terminal metal parts 11, 12and the heater terminal metal parts 16, 17 in the separator 31,therefore, the separator 31 is fixed and hence cannot be adequatelymoved. Consequently, defects such as that the first and second sensorterminal metal parts 11, 12 are ruptured, that the heater 15 is bent,and that connections between the electrode pads 15 e, 15 f of the heater15 and the heater terminal metal parts 16, 17 are broken may occur.

By contrast, in the configuration where the butting step is firstconducted and the deforming step is then conducted as in the embodiment,even when stresses are applied to the first and second sensor terminalmetal parts 11, 12, the heater terminal metal parts 16, 17, the heater15, and the like in the butting step, the separator 31 in the looselyinserted state is adequately moved to eliminate or reduce the stresses.Therefore, a defect such as bending of the heater or rupture of theterminal metal parts hardly occurs.

Next, as shown in FIG. 13, the portion of the second outer tube potion23 of the metal outer tube 21 which is positioned around the grommet 51is caulked by a caulking jig CL2, so that the metal outer tube 21, theleas wire 13, and the like are airtightly sealed.

As shown in FIG. 14, the connecting portion 3 d of the metal shell 3 andthe tip end portion 22 a of the metal outer tube 21 which are alreadyprovisionally connected to each other are airtightly connected by laserwelding, thereby completing the oxygen sensor 1.

In the oxygen sensor 2 of the embodiment, as shown in FIG. 12( b), a gapis formed between the flange portion 34 of the separator 31 and a flangesurrounding portion 23 c of the metal outer tube 21 which is positionedaround the flange portion 34. The outer diameter d2 (=14 mmφ) of themetal tube portion 42 of the pressing metal part 41 is slightly largerthan the outer diameter d1 (=13.4 mmφ) of the flange portion 34. In thecase where the oxygen sensor 1 is mounted on an automobile to be used,even when flying stone strikes against the flange surrounding portion 23c of the metal outer tube 21 and the metal outer tube 21 is largelydepressed, therefore, the depressed metal outer tube 21 first collideswith the metal tube portion 42 of the pressing metal part 41 before itcollides with the flange portion 34 made of ceramic. Therefore, thecollision is buffered, and a defect that the separator 31 is broken orcracked as a result of the hit of stone against the portion can beprevented from occurring.

In the above, the invention has been described by way of the embodiment.However, the invention is not restricted to the embodiment. It is amatter of course that the invention can be applied while beingadequately modified without departing from the spirit of the invention.

For example, the embodiment in which the inner projection 24 is disposedin the four places in the circumferential direction of the metal outertube 21 has been described. It is only necessary to dispose the innerprojection in three places. By contrast, a step portion may be disposedso that an inclined face is formed over the whole of the metal outertube in the circumferential direction.

In the embodiment described above, the pressing metal part 41 has aconfiguration in which the J-shaped elastic holding portion 43 is formedin the four places in the circumferential direction of the rear end ofthe metal tube portion 42. It is requested to form the J-shaped elasticholding portion in three or more places at regular intervals.Alternatively, a pressing metal part may be used which, in place of theJ-shaped elastic holding portion, has an L-shaped elastic holdingportion that elongates radially inward from the rear end of the metaltube portion 42, and that is then bent to elongate toward the tip end.Alternatively, in place of the pressing metal part, a cylindrical rubbermember having an inner diameter which is smaller than the outer diameterof the tip end side portion 33 of the separator 31, and an outerdiameter which, when the member is attached to the tip end side portion33, is smaller than the inner diameter of the metal outer tube 21 may beused. When the cylindrical rubber member is used, in accordance with theformation of the deformed portion 23 b of the metal outer tube 21 in thedeforming step, the member is deformed to press the tip end side face 34b of the flange portion 34 of the separator 31 toward the rear end. Whenthe cylindrical rubber member is used, the handling is facilitated.

Alternatively, the elastic member 1006 which is used in theabove-described conventional art may be used. In this case also, whenthe outer-tube butting face 34 a in which the diameter is made larger asfurther advancing toward the tip end side is disposed in the separator31, and the flange butting face 24 b forming an inclined face which ismore radially outward positioned as further advancing toward the tip endis in the metal outer tube 21, it is possible to attain the effect that,when the separator 31 is to be fixed to the metal outer tube 21, theaxis 31 x of the separator 31 can be moved so as to coincide with theaxis 21 x of the metal outer tube 21 (see FIG. 9).

In the embodiment, the oxygen sensor 1 has been described. The inventioncan be applied also to other gas sensors such as a NOx sensor and an HCsensor. In the embodiment described above, the sensor element having ashape in which the tip end is closed is used as the oxygen sensorelement 2. The shape can be adequately changed in accordance with theobject to be detected. For example, a plate-like sensor element may beused. Since it is requested only that the outer-tube butting face 34 acan be formed in the separator 31 and the flange butting face 24 b canbe formed in the metal outer tube 21, the invention can be applied alsoto a sensor in which a heater is not used. In the embodiment, both ofthe outer-tube butting face 34 a of the separator 31 and the flangebutting face 24 b of the metal outer tube 21 are formed as a taperedface in which the diameter is made larger as further advancing towardthe tip end. Alternatively, while a tapered face in which the diameteris made larger as further advancing toward the tip end may be formed inone of the separator 31 and the metal outer tube 21, the other one maybe caused to butt against the tapered face. According to theconfiguration, it is expected to attain an effect that the position ofthe separator 31 can be adequately determined with respect to the metalouter tube 21.

Although the invention has been described in detail and with referenceto a particular embodiment, it will be obvious to those skilled in theart that various changes and modifications may be made without departingthe spirit and scope of the invention.

The present application is based on a Japanese patent application(Application No. 2002-211687) filed Jul. 19, 2002, and its disclosure isincorporated herein by reference.

1. A sensor comprising: a sensor element; a metal shell which holds saidsensor element; one or more sensor terminal members which areelectrically connected to said sensor element, and which elongate fromsaid sensor element toward a rear end; a metal outer tube which isconnected to said metal shell at a tip end portion of said metal outertube itself; and an electrically insulative separator which is housedinside said metal outer tube, in which said sensor terminal members arepositioned, and which provides at least one of insulation between saidsensor terminal members, and insulation between said sensor terminalmembers and said metal outer tube, wherein said separator has: a rearend side portion; and a flange portion which is positioned on a tip endside with respect to said rear end side portion, and which is larger indiameter than said rear end side portion, said metal outer tube has astep portion or an inner projection which butts against said flangeportion of said separator, at least one of an outer-tube butting face ofsaid flange portion of said separator, and a flange butting face of saidstep portion or said inner projection of said metal outer tube forms aninclined face which is more radially outward positioned as furtheradvancing toward said tip end, said outer-tube butting face buttingagainst said step portion or said inner projection of said metal outertube and being positioned on a side of said rear end, said flangebutting face butting against said outer-tube butting face of said flangeportion of said separator, and said separator is held by said metalouter tube in a state where said separator is pressed toward said rearend, wherein a gap is present between the flange portion of theseparator and a flange surrounding portion of the metal outer tube whichis positioned around the flange portion.
 2. The sensor according toclaim 1, wherein both of the outer-tube butting face of said flangeportion of said separator, and the flange butting face of said stepportion or said inner projection of said metal outer tube form aninclined face which is more radially outward positioned as furtheradvancing toward said tip end.
 3. The sensor according to claim 1,wherein said flange portion of said separator has a tip end side facefacing said tip end side, and said sensor comprises a pressing memberwhich is held inside said metal outer tube, and which butts against saidtip end side face of said flange portion to press said separator towardsaid rear end, said pressing member being in point contact with said tipend side face as seen in a radial direction.
 4. The sensor according toclaim 1, wherein said sensor element is a cylindrical gas sensor elementin which a tip end side is closed, said sensor has: a rod heater whichis inserted into a bottomed hole of said gas sensor element; and one ormore heater terminal members which are electrically connected to saidheater, and said separator is a separator which provides insulationbetween said sensor terminal members and said heater terminal members.5. The sensor according to claim 1, wherein said pressing memberradially inward presses said separator.
 6. A sensor comprising: a sensorelement; a metal shell which holds said sensor element; one or moresensor terminal members which are electrically connected to said sensorelement, and which elongate from said sensor element toward a rear end;a metal outer tube which is connected to said metal shell at a tip endportion of said metal outer tube itself; and an electrically insulativeseparator which is housed inside said metal outer tube, in which saidsensor terminal members are positioned, and which provides at least oneof insulation between said sensor terminal members, and insulationbetween said sensor terminal members and said metal outer tube, whereinsaid sensor has a pressing member which holds said separator whileaxially rearward pressing said separator against said metal outer tube,said metal outer tube has a first reduced-diameter portion whichradially inward protrudes, and which butts against said separator, and asecond reduced-diameter portion which butts against said pressingmember, said separator has, between said first reduced-diameter portionand said second reduced-diameter portion, a flange portion which buttsat a rear end side against said metal outer tube while butting at a tipend side against said pressing member, and at least one of said firstreduced-diameter portion of said metal outer tube and said flangeportion of said separator butts against another one via an inclined facewhich is more radially outward positioned as further advancing towardsaid tip end.
 7. The sensor according to claim 6, wherein said pressingmember radially inward presses said separator.
 8. A sensor comprising: asensor element; a metal shell which holds said sensor element; one ormore sensor terminal members which are electrically connected to saidsensor element, and which elongate from said sensor element toward arear end; a metal outer tube which is connected to said metal shell at atip end portion of said metal outer tube itself; and an electricallyinsulative separator which is housed inside said metal outer tube, inwhich said sensor terminal members are positioned, and which provides atleast one of insulation between said sensor terminal members, andinsulation between said sensor terminal members and said metal outertube, wherein said sensor has a pressing member which holds saidseparator while axially rearward pressing said separator against saidmetal outer tube, said metal outer tube has a first reduced-diameterportion which radially inward protrudes, and which butts against saidseparator, and a second reduced-diameter portion which holds saidpressing member while radially inward pressing said pressing member, andsaid separator has, between said first reduced-diameter portion and saidsecond reduced-diameter portion, a flange portion which butts at a rearend side against said metal outer tube while butting at a tip end sideagainst said pressing member.
 9. The sensor according to claim 8,wherein said pressing member radially inward presses said separator. 10.A method for producing a sensor, said sensor comprising: a sensorelement; a metal shell which holds said sensor element; one or moresensor terminal members which are electrically connected to said sensorelement, and which elongate from said sensor element toward a rear end;a metal outer tube which is connected to said metal shell at a tip endportion of said metal outer tube itself; and an electrically insulativeseparator which is housed inside said metal outer tube, said separatorincluding: a rear end side portion which is positioned on a side of saidrear end; a tip end side portion which is positioned on a side of a tipend; and a flange portion which is positioned at a middle between saidrear end side portion and said tip end side portion, which is larger indiameter than said rear end side portion and said tip end side portion,and which has a tip end side face facing said tip end side between saidflange portion and said tip end side portion, and a rear end side facefacing said rear end side between said flange portion and said rear endside portion, said sensor terminal members being positioned inside, saidseparator providing at least one of insulation between said sensorterminal members, and insulation between said sensor terminal membersand said metal outer tube, said metal outer tube having a step portionor an inner projection which butts against said rear end side of saidflange portion of said separator, said sensor having a pressing memberwhich presses said separator toward said rear end, wherein said methodcomprises: a butting step of, in a state where said sensor terminalmembers are positioned inside said separator, said pressing member isheld by an outer periphery of said tip end side portion of saidseparator, and said flange portion of said separator and said stepportion or said inner projection of said metal outer tube butt againsteach other, moving at least one of said metal outer tube and said metalshell in a direction along which said metal outer tube and said metalshell approach each other, thereby causing said tip end portion of saidmetal outer tube to butt against said metal shell; and a deforming stepof, in a state where said sensor terminal members are positioned inside,said flange portion of said separator in which said pressing member isheld by said outer periphery of said tip end side portion, and said stepportion or said inner projection of said metal outer tube butt againsteach other, and said pressing member butts against said tip end sideface of said flange portion of said separator, radially inward pressinga portion of said metal outer tube to form a deformed portion whichinward protrudes, said portion being positioned in a radially outer sideof said pressing member, and deform also said pressing member so thatsaid pressing member presses said separator toward said rear end. 11.The method for producing a sensor according to claim 10, wherein saidrear end side face of said flange portion of said separator forms aninclined face which is more radially outward positioned as furtheradvancing toward said tip end, and said step portion or said innerprojection of said metal outer tube has a flange butting face forming aninclined face which butts against said rear end side face of saidseparator, and which is more radially outward positioned as furtheradvancing toward said tip end.
 12. The method for producing a sensoraccording to claim 10, wherein said pressing member has: a metal tubeportion having an inner diameter which is larger than an outer diameterof said tip end side portion of said separator, and an outer diameterwhich is smaller than an inner diameter of said metal outer tube; and anelastic holding portion which, when said metal tube portion is attachedto said tip end side portion of said separator, elastically buttsagainst said tip end side portion of said separator inside said metaltube portion, to hold said metal tube portion to said separator, and inaccordance with the formation of said deformed portion of said metalouter tube in said deforming step, said tip end side face of said flangeportion of said separator is pressed toward said rear end by said rearend of said metal tube portion.
 13. The method for producing a sensoraccording to claim 12, wherein said metal tube portion of said pressingmember has a rear end portion which is curved inward or outward in aradial direction.
 14. The method for producing a sensor according toclaim 12, wherein said elastic holding portion of said pressing memberis a J-shaped elastic holding portion which is positioned in said rearend of said metal tube portion, which elongates radially inward, andwhich is gradually changed in direction to elongate toward said tip endto be curved into a substantially J-like shape.
 15. The method forproducing a sensor according to claim 10, wherein said sensor element isa cylindrical gas sensor element in which a tip end side is closed, saidsensor has: a rod heater which is inserted into a bottomed hole of saidgas sensor element; and one or more heater terminal members which areelectrically connected to said heater, said separator holds insulationbetween said sensor terminal members and said heater terminal members,said butting step is conducted in a manner that, in a state where saidseparator is loosely inserted into said metal outer tube, at least oneof said metal outer tube and said metal shell is moved in a directionalong which they approach each other, to cause said tip end portion ofsaid metal outer tube to butt against said metal shell, and said heateris inserted into said gas sensor element held by said metal shell, andsaid deforming step is conducted after said butting step.
 16. The methodfor producing a sensor according to claim 15, wherein said butting stepincludes an inserting and positioning step of positioning and insertinga tip end of said heater to be guided into a rear end opening of saidgas sensor element, said tip end further protruding toward said tip endthan said tip end portion of said metal outer tube.
 17. The method forproducing a sensor according to claim 16, wherein said inserting andpositioning step is conducted by guiding a part of a portion of saidheater which further protrudes toward said tip end than said tip endportion of said metal outer tube, by a chuck device, and adjusting aposition of said tip end of said heater.
 18. An assembly of a separatorand a pressing member which is to be used in a sensor, said sensorcomprising: a sensor element; a metal shell which holds said sensorelement; one or more sensor terminal members which are electricallyconnected to said sensor element, and which elongate from said sensorelement toward a rear end; a metal outer tube which is connected to saidmetal shell at a tip end portion of said metal outer tube itself; and anelectrically insulative separator which is housed inside said metalouter tube, said separator including: a rear end side portion which ispositioned on a side of said rear end; a tip end side portion which ispositioned on a side of a tip end; and a flange portion which ispositioned at a middle between said rear end side portion and said tipend side portion, which is larger in diameter than said rear end sideportion and said tip end side portion, and which has a tip end side facefacing said tip end side between said flange portion and said tip endside portion, and an outer-tube butting face facing said rear end sidebetween said flange portion and said rear end side portion, said sensorterminal members being positioned inside, said separator providing atleast one of insulation between said sensor terminal members, andinsulation between said sensor terminal members and said metal outertube, said metal outer tube having a step portion or an inner projectionwhich has a flange butting face butting against said outer-tube buttingface of said flange portion of said separator, said sensor having apressing member which presses said separator toward said rear end,wherein said pressing member has: a metal tube portion having an innerdiameter which is larger than an outer diameter of said tip end sideportion of said separator, and an outer diameter which is smaller thanan inner diameter of said metal outer tube; and an elastic holdingportion which is placed inside said metal tube portion, said elasticholding portion elastically butts against said-tip end side portion ofsaid separator, and said pressing member is held by said separator.